Hard Code

This post continues from the last one . I will try to complete the lead microservice in this post. I will be focusing primarily on the CRUD operation. In CRM applications, that is the primary set of operations. I will start by creating the exception class. Later I would show how to use this exception class and Spring Rest exception handling and build a robust error handling around the API calls. Listing 1 - BusinessException.java Next step would be to introduce the service class. Since this is CRUD most of the functionality can be encapsulated in an abstract parent service class. Any specific feature like convert lead to opportunity can be implemented in the LeadService class. Listing 2 - AbstractBaseBusinessDelegate.java And then finally the LeadService implementation class is shown in Listing 3. Listing 3 - LeadBusinessDelegate.java Note that this code will not compile. In order to get this to compile, you will need to add 2 new dependencies for the...

This is a continuation of my previous post where I listed the key domain components of CRM. For sake of simplicity, I will focus on just two key components - Lead and Opportunity respectively. These two modules will help me explore end to microservice implementation. I will be primarily using Spring framework's support to deliver the microservices. I am deliberating on a nice interesting Javascript framework for the front end. More on this later. Goal For the time being, I am just going to focus on building the backend and cloud enable it. Then slowly I am going to add the front end and security to the backend and front end. I will also explore the complete Sping Cloud gamut of projects and beyond. I will then deliberate on cloud-native applications, transactions and actually making this application suitable to run on virtually any cloud. I will also explore cloud and microservices application design patterns. Last but not the least we also need to check where this application...

In my previous posts, I have shared some theory regarding microservices. But it's time to start some implementation. I love to write code and see and feel things working. So I will start a series to refactor a monolithic CRM system and transform it into microservices based flexible software. Big ball of mud. Customer Relationship Management(CRM) is that giant software which existed since time immemorial and is used by all companies in some form or shape. Big enterprises will buy CRM software (also known as packages) from top CRM vendors like Oracle, SAP, Salesforce etc and then employ an army of consultants to try and implement it. Most of the classic CRM systems in the market today, even if deployed on the cloud are the big monolithic ball of mud. They are the gigantic piece of software with the huge feature set. Most often those requirements are surplus to the requirement or they will not fit into the processes of the company. So the company has to hire these certified consu...

The 12-factor app guideline was published by Heroku the platform as a service (PaaS) provider (now a part of Salesforce.com). These were a set of principles/best practices that one needed to follow to build applications on the Heroku PaaS. Over time, this has become the de-facto standard for building web applications on the cloud or more precisely cloud-native applications. The original 12-factor app guideline is available at 12factor.net and was not really meant for microservices. In this post, I will try to go over the 12-factor app guidelines and check how they fit into microservices architecture. 1 – Codebase One codebase tracked in revision control, many deploys The application codebase should be maintained in a version control system (VCS).All developers should have easy access to VCS.There is only one codebase per application in the VCS, but there can be multiple deployment copies of this application codebase. For example, an application can be deployed in di...

A real life story In my previous post introducing microservices , I wrote about this insurance product I was working on at the beginning of my IT career. It started off very simple as a layered application. Well it was not simple, the learning curve with J2EE of that time was indeed high. Just like microservices, it was all shiny new thing. The application started with just a couple of us. Then we started adding features. The product was sold. I was happy, I went to install and implement it at customer sites. It was fun. Then customers demanded more and more features. New features were also required to address new business challenges and compete with established players. So we kept adding more bricks and mortar on that same structure. 2+ years flew by and I realized that we have about 20 odd modules, 500+ tables, and nearly a team of 100+. We had several customers in the US and elsewhere using this product. It was really a big success in such a short span of time. But I also rea...

The whole idea of microservices revolves around building a large application from a set of small modules which are composed around business functions.Let me share one concrete example to understand this better. Figure 1, shows the classic layered architecture that I was introduced to back in 2001 when I was building a large product for the insurance providers. Figure 1 - Classic Architecture of the Insurance Product Only three key modules from the product are shown here for simplicity. This was a very large product with several other modules. The UI was developed using JSPs (HTML, Stylesheets, Javascript). The UI was packed in a war file. The business logic was written using stateless session beans. The data access layer was all entity beans. The EJBs and the war file was then packaged inside an ear file and finally deployed in a Java application server. This application was also modular, but horizontally.So that ear file contained everything – the UI, business logic, the data...

Microservices is still a new and evolving subject. Hence, there is a lot of confusion regarding the term and concepts around it. A lot of clarity is starting to emerge of late, as teams try to embrace this new architectural style.I know people tend to think and preach that since the application that they have developed recently expose few REST web services, they are doing microservices. Some have even installed API Gateway in front of the Rest web services layer. Trust me this is still a layered cake classic architecture which is just opposite of microservices. The naysayers call this a monolith . I have some reservations against that word. Later I will explain the reason for the same. Figure 1 - Classic Architecture Microservices is an architectural style. In this style, an application (generally large and complex one) is built using a small set of loosely coupled services which implement specific business capabilities. Well, we have been doing this for years, haven't w...